In many industrial processes a process gas containing pollutants is generated. One such industrial process is the combustion of a fuel, such as coal, oil, peat, waste, and the like, in a combustion plant, such as a power plant, whereby a hot process gas is generated. This hot process gas is often referred to as a flue gas. The flue gas contains various pollutants including acid gases, such as sulphur dioxide, SO2. It is necessary to remove as much of the acid gases as possible from the flue gas before the flue gas may be emitted to the ambient air. Another example of an industrial process in which a process gas containing pollutants is generated is the electrolytic production of aluminium from alumina. In that process, a process gas containing sulphur dioxide, SO2, is generated within venting hoods of the electrolytic cells.
U.S. Pat. No. 5,484,535 discloses a seawater scrubber. In the seawater scrubber seawater taken from the ocean is mixed with a flue gas generated by a boiler. In the seawater scrubber, sulphur dioxide, SO2, is absorbed in the seawater and forms sulphite and/or bisulphite ions. Effluent seawater from the seawater scrubber is forwarded to an aeration pond. Air is bubbled through the effluent seawater in the aeration pond for purposes of oxidizing, by means of oxygen gas contained in the air, sulphite and/or bisulphite ions to inert sulphate ions that may be released back to the ocean together with the effluent seawater.
Certain metals may be used to catalyze the above-described oxidation reactions occurring in effluent seawater aeration systems. As such, modern aeration systems used for oxidizing effluent seawater may dose the effluent seawater with metal by placing sheets or bars of such metals, such as iron sheets or iron bars, in the aeration system. Iron sheets or iron bars are placed in the aeration systems to catalyze the oxidation reactions in the effluent seawater since such metals are usually not present in the effluent seawater in sufficient quantity for this purpose.